Discovery of Novel Imidazopyridine GSK-3ß Inhibitors Supported by Computational Approaches.

The interest of research groups and pharmaceutical companies to discover novel GSK-3ß inhibitors has increased over the years considering the involvement of this enzyme in many pathophysiological processes and diseases. Along this line, we recently reported on 1H-indazole-3-carboxamide (INDZ) derivatives 1-6, showing good GSK-3ß inhibition activity. However, they suffered from generally poor central nervous system (CNS) permeability. Here, we describe the design, synthesis, and in vitro characterization of novel imidazo[1,5-a]pyridine-1-carboxamide (IMID 1) and imidazo[1,5-a]pyridine-3-carboxamide (IMID 2) compounds (7-18) to overcome such liability. In detail, structure-based approaches and fine-tuning of physicochemical properties guided the design of derivatives 7-18 resulting in ameliorated absorption, distribution, metabolism, and excretion (ADME) properties. A crystal structure of 16 in complex with GSK-3ß enzyme (PDB entry 6Y9S) confirmed the in silico models. Despite the nanomolar inhibition activity, the new core compounds showed a reduction in potency with respect to INDZ derivatives 1-6. In this context, Molecular Dynamics (MD) and Quantum Mechanics (QM) based approaches along with NMR investigation helped to rationalize the observed structure activity relationship (SAR). With these findings, the key role of the acidic hydrogen of the central core for a tight interaction within the ATP pocket of the enzyme reflecting in good GSK-3ß affinity was demonstrated.

Optimization of Indazole-Based GSK-3 Inhibitors with Mitigated hERG Issue and In Vivo Activity in a Mood Disorder Model.

Bipolar disorders still represent a global unmet medical need and pose a requirement for novel effective treatments. In this respect, glycogen synthase kinase 3ß (GSK-3ß) aberrant activity has been linked to the pathophysiology of several disease conditions, including mood disorders. Therefore, the development of GSK-3ß inhibitors with good in vivo efficacy and safety profile associated with high brain exposure is required. Accordingly, we have previously reported the selective indazole-based GSK-3 inhibitor 1, which showed excellent efficacy in a mouse model of mania. Despite the favorable preclinical profile, analog 1 suffered from activity at the hERG ion channel, which prevented its further progression. Herein, we describe our strategy to improve this off-target liability through modulation of physicochemical properties, such as lipophilicity and basicity. These efforts led to the potent inhibitor 14, which possessed reduced hERG affinity, promising in vitro ADME properties, and was very effective in a mood stabilizer in vivo model.

Virtual Screening Approach and Investigation of Structure-Activity Relationships To Discover Novel Bacterial Topoisomerase Inhibitors Targeting Gram-Positive and Gram-Negative Pathogens.

Bacterial resistance is increasing rapidly, requiring urgent identification of new antibacterial drugs that are effective against multidrug-resistant pathogens. Novel bacterial topoisomerase inhibitors (NBTIs) provide a new strategy for investigating the well-validated DNA gyrase and topoisomerase IV targets while preventing cross-resistance issues. On this basis, starting from a virtual screening campaign and subsequent structure-based hit optimization guided by X-ray studies, a novel class of piperazine-like NBTIs with outstanding enzymatic activity against Staphylococcus aureus and Escherichia coli DNA gyrase and topoisomerase IV was identified. Notably, compounds (±)-33, (±)-35, and (±)-36 with potent and balanced multitarget enzymatic profiles exhibited excellent efficacy against selected Gram-positive and Gram-negative pathogens, as well as clinically relevant resistant strains. Overall, the new NBTI chemotype described herein, owing to the broad-spectrum antibacterial activity and favorable in vitro safety profile, might serve as a basis for the development of novel treatments against serious infections.

Targeting Serotonin 2A and Adrenergic α1 Receptors for Ocular Antihypertensive Agents: Discovery of 3,4-Dihydropyrazino[1,2-b]indazol-1(2H)-one Derivatives.

Glaucoma affects millions of people worldwide and causes optic nerve damage and blindness. The elevation of the intraocular pressure (IOP) is the main risk factor associated with this pathology, and decreasing IOP is the key therapeutic target of current pharmacological treatments. As potential ocular hypotensive agents, we studied compounds that act on two receptors (serotonin 2A and adrenergic α1 ) linked to the regulation of aqueous humour dynamics. Herein we describe the design, synthesis, and pharmacological profiling of a series of novel bicyclic and tricyclic N2-alkyl-indazole-amide derivatives. This study identified a 3,4-dihydropyrazino[1,2-b]indazol-1(2H)-one derivative with potent serotonin 2A receptor antagonism, >100-fold selectivity over other serotonin subtype receptors, and high affinity for the α1 receptor. Moreover, upon local administration, this compound showed superior ocular hypotensive action in vivo relative to the clinically used reference compound timolol.

Hit Optimization of 5-Substituted-N-(piperidin-4-ylmethyl)-1H-indazole-3-carboxamides: Potent Glycogen Synthase Kinase-3 (GSK-3) Inhibitors with in Vivo Activity in Model of Mood Disorders.

Novel treatments for bipolar disorder with improved efficacy and broader spectrum of activity are urgently needed. Glycogen synthase kinase 3ß (GSK-3ß) has been suggested to be a key player in the pathophysiology of bipolar disorder. A series of novel GSK-3ß inhibitors having the common N-[(1-alkylpiperidin-4-yl)methyl]-1H-indazole-3-carboxamide scaffold were prepared taking advantage of an X-ray cocrystal structure of compound 5 with GSK-3ß. We probed different substitutions at the indazole 5-position and at the piperidine-nitrogen to obtain potent ATP-competitive GSK-3ß inhibitors with good cell activity. Among the compounds assessed in the in vivo PK experiments, 14i showed, after i.p. dosing, encouraging plasma PK profile and brain exposure, as well as efficacy in a mouse model of mania. Compound 14i was selected for further in vitro/in vivo pharmacological evaluation, in order to elucidate the use of ATP-competitive GSK-3ß inhibitors as new tools in the development of new treatments for mood disorders.

Discovery and pharmacological profile of new 1H-indazole-3-carboxamide and 2H-pyrrolo[3,4-c]quinoline derivatives as selective serotonin 4 receptor ligands.

Since the discovery of the serotonin 4 receptor (5-HT(4)R), a large number of receptor ligands have been studied. The safety concerns and the lack of market success of these ligands have mainly been attributed to their lack of selectivity. In this study we describe the discovery of N-[(4-piperidinyl)methyl]-1H-indazole-3-carboxamide and 4-[(4-piperidinyl)methoxy]-2H-pyrrolo[3,4-c]quinoline derivatives as new 5-HT(4)R ligands endowed with high selectivity over the serotonin 2A receptor and human ether-a-go-go-related gene potassium ion channel. Within these series, two molecules (11 ab and 12 g) were identified as potent and selective 5-HT(4)R antagonists with good in vitro pharmacokinetic properties. These compounds were evaluated for their antinociceptive action in two analgesia animal models. 12 g showed a significant antinociceptive effect in both models and is proposed as an interesting lead compound as a 5-HT(4)R antagonist with analgesic action.

New anti-viral drugs for the treatment of the common cold.

Human Rhinovirus (HRV) is the most important aetiologic agent of common cold in adults and children. HRV is a single-stranded, positive sense RNA virus and, despite the high level of conservation among different serotypes, sequence alignment of viral protease 3C with mammalian protease reveals no homology. Thus, protease 3C is an optimal target for the development of anti-HRV agents. In the present work we investigated the design, the synthesis and the development of new potential reversible inhibitors against HRV protease 3C. Docking studies on the crystallized structure of HRV2 protease 3C led us to the design and the synthesis of a series of 3,5 disubstituted benzamides able to act as analogues of the substrate. We also developed 1,3,5 trisubstituted benzamides where aromatic substitutions on the aryl ring led us to investigate the importance of pi-pi interaction on the stabilization of protease 3C-inhibitor complex. All structures were tested for enzymatic inhibition on HRV14 protease 3C. Results highlighted the inhibitory activity of compounds 13, 14, and 20 (91%, 81%, and 85% at 10 microM, respectively), with the latter exhibiting an ID(50) (dose that inhibits 50% of the viral cytopathic effect) on HRV-14=25 microg/ml.